## Gating Current

NMODL and the Channel Builder.
Kahlig

### Gating Current

I would like to know if anyone has attemped to measure the gating current that would result from a set of rate constants defining a kinetic scheme.

I have a channel described by a kinetic scheme such as
Transition 1
~ A <--> B <alpha1, beta1>
Transition 2
~B <--> C <alpha2, beta2>
where alpha and beta have the units 1/ms
and the states A, B, and C have the usual units of mol/cm2
The total gating current is 30% from transition 1 and 70% from transtion 2. Total gating current would be assigned.

I would like to measure the gating current associated with the transitions (such as in the response to a voltage step).

I envision something like:

Total Net fraction of channels that moved through Transition 1 is
T1=(alpha1[A]-beta1)*dt*(total membrane area)
gating current of transition 1 is
gT1=(T1 channels)*(0.3*total gating current)

and likewise for transition 2
T2=(alpha2-beta2[C])*dt*(total membrane area)
gT2=(T2 channels)*(0.7*total gating current)

However, I'm not sure this would work and even if it did, I'm sure it is slightly computationally demanding to peform these calculations every time step. Has anyone attemped to make gating current measurements previously and and if so is there a better way.

Thanks,
Kris Kahlig